One or more main engines of an aircraft, or a diesel tug, can be used to move the aircraft between an airport terminal (or stand) and a holding area near a runway. However, the noise and pollution (particularly NOx and CO) generated by pushback and taxi movements are of increasing concern to communities near the airport. Additionally, on-ground fuel consumption is of growing concern to airline companies concerned with fuel costs. For example, taxiing aircraft can contribute up to 54% of the total airport NOx emissions and 25% of the total airport CO emissions.
One solution to the above problems is the use of electric tugs motivated by a set of batteries and allowing the aircraft engines to remain off until the aircraft has been towed to a pre-flight position. Unfortunately, it can be necessary to operate an auxiliary power unit (APU) in the tail of the aircraft to generate electricity and pneumatic power for environmental control systems (ECS) such as air conditioning, contributing substantially to pollution and noise at the airport. Also, the batteries of the electric tug can lack the reserve power necessary to displace the APU, and can require charging several times per day.